How to Make Dextrin Coated Paper for the Toner Transfer method of making PCBs
Dextrin coated paper is the very best paper to use for the Toner Transfer method of creating Printer Circuit Boards (PCBs).
Why Dextrin Coated Paper it so good?
- The etching mask is printed on the dextrin coated side of the paper using a laser printer
- The mask is then bonded to a PCB using a laminator (ideally) or an iron (ugh).
- Then the board with the paper still attached is placed in warm water.
- The dextrin coating immediately starts to dissolve and in 1 – 10 minutes it will just come off completely without any problems whatsoever. Note that Press-n-Peel takes just a minute to float off. This dextrin coated paper with the waterproofer will take longer – about 10 minutes. No big deal just give it time and it will come right off.
- The toner is left 100% bonded to the PCB.
- If you don’t use dextrin coated paper then you may have very inconsistent results (read missing traces) because you had to fight with stuck on paper, and will have much frustration and wasted time. After all, regular paper is made up of millions of fibers, and toner is plastic. If you heat the two and press them together they will not want to part… Many people claim that “such and such paper works fine”, but mostly its a pain!
A Warning: You will probably not save much money (and definitely not time) making your own coated paper, particularly if you only make a small batch. If however you enjoy making a potentially superior tool with your own hands, and want the satisfaction of being independent then this can be good for you. Otherwise just buy a commercial product like Press-n-Peel! Read on and see.
Making Dextrin Coated Paper
Note that I did not invent this method, but I have improved it I think, although the original article used a rubber roller that may give you a thinner coat.
- White heavy weight paper that has a smooth surface. I used HP Laser Broshure paper because I had it, and it worked well and is very smooth. A smooth paper allows finer printing. A stiffer paper is better when aligning double sided boards. You might look for something cheaper though.
- A box of corn starch to make Dextrin.
- A sheet pan and spatula.
- An air-proof container to hold the finished Dextrin powder.
- A foam trim roller. The one I used was the white 6-inch QUALI-TECH from Home Depot. It should have a smooth surface.
- A roller pan.
- A large trash bag or sheet of plastic.
- Rubber Gloves.
- A respirator or very good ventilation.
The first step is to make Dextrin powder by heating corn starch:
- Spread a box of corn starch on a cookie sheet that has sides or ½ sheet pan (or large baking dish). A large surface area will make it heat more evenly.
- Place in a 400 degree oven for 2 ½ hours, stirring and re-leveling every 20-30 minutes with a spatula until all the white specks are gone. The fine powder will be a medium tan color when it’s done, it should not be burned. (Your oven temp may vary).
- Cool and place in an air-tight container, label it Dextrin. You will have enough for a lifetime supply.
To make 4+ oz of Dextrin Glue (enough to coat 14+ pages)
- Add 5 oz water to a cooking pot.
- Add 3 level tablespoons of dextrin powder.
- Whisk until it boils, then simmer for 5 more minutes while whisking. You are just removing any lumps.
- Cool and place in an airtight container.
- There is no need to “reduce” the Dextrin glue. It should be thin!
- The dextrin glue is quick to make, so make just enough for the batch of paper you are making. It doesn’t store very well (it can mold).
First waterproof the paper:
- Place a large unfolded trash bag on a table outdoors.
- Put on a respirator, or make sure there is good airflow, and wear rubber gloves. You will be working with the waterproofing spray for several minutes…
- Start off by spraying both sides of each sheet of paper with the Camp Dry waterproofer.
- You can wipe each side with a saturated paper towell to even it up.
- Make sure the paper is completely saturated on both sides, it should be just about transparent.
- Do not omit this waterproofing step! If you try to coat paper with dextrin without this it will just curl up and be totaly unusable! I tried…
- Lay the waterproofed sheets on flat surfaces and allow to dry separately overnight. I used some old window screens for this. You do NOT want to do this inside your house.
- The next day – coat the paper with dextrin. This can be done indoors, in a dust-free environment. (In the garage with sawdust wouldn’t be great).
- Pour the dextrin glue into a small roller tray.
- Use a foam trim roller to quickly apply a thin coat to one side of a sheet of your waterproofed paper.
- The dextrin should be thin! It may become tacky very quickly while you are rolling it on, so do not keep going over it – you want it smooth.
- Lay each sheet on flat a surface until completely dry. It will not dry perfectly flat, but this much better than trying to coat paper without the waterproofer! The curling is caused when the dextrin shrinks when it dries.
- After all pages are completely dry you will want to store them flat, perhaps with a weight on them.
It would be good to test making the dextrin glue even thinner by starting with 6 oz or more of water. The slight curling may be lessened.
Also see my articles about Perfect single or double sided PCBs with the Toner Transfer Method and DIY Riveted Vias.